JAKARTA - Indonesia kept seven airports closed on Monday after an eruption of Anak Krakatau sent volcanic ash through the airspace around Jakarta and disrupted about 2,300 flights. The eruption had eased, but authorities warned that the volcano remained active and could erupt again.

The Geological Agency said the continuous eruption lasted about 25 hours and produced a fountain of lava and a boom heard roughly 700 kilometres away. On Monday, the volcano was still producing moderate, intermittent eruptions, dark ash emissions and small local earthquakes.

AirNav Indonesia detected ash in the airspace around Jakarta and several other cities. Four major commercial airports, including Soekarno-Hatta and Halim Perdanakusuma, were among those affected. The Transportation Ministry said about 270,337 passengers had been affected by the disruption.

The disruption extended beyond aviation. Schools in parts of Jakarta, West Java, Banten and Lampung were allowed to move temporarily to remote learning to reduce children's exposure to volcanic ash. Authorities were monitoring the air and the possibility of additional emissions.

Indonesia's Geological Agency said the probability of further eruptions remained high, with volcanic bombs, heavy ashfall and possible lava flows among the main hazards if sustained activity returned. Anak Krakatau sits in the Sunda Strait between Java and Sumatra and is the offspring of the volcano associated with the 1883 Krakatau eruption.